Light emitted from a display device in operation is provided by a back light source. Backlight sources in the prior art mainly comprises side type backlight source and direct type backlight source; the principle of the backlight source is providing light to a display device, which light is emitted from light source elements set in a backboard of the backlight source.
Defects of the prior art are that: the brightness adjustment of the display device in the prior art is realized by adjusting the electric current of all the light source elements in the backlight source, the adjustment range is relatively small; moreover, even in a situation that a low brightness is required for the display device, all the light source elements are still in working condition, affecting the service life of the backlight source.